1. Field of the Invention
This invention relates to a non-contact type IC card capable of transferring data at a high rate and having excellent ambient resistance and plug-in/out resistance, an electromagnetic coupling connector used for the IC card, and an IC card system. More particularly, the present invention relates to an electromagnetic coupling system between an IC card and a terminal equipment.
2. Description of the Related Art
A memory card as one of the kinds of IC cards has been used recently as a data base of electronic notebooks, an external storage medium of various personal computers, an add-on memory, and so forth, and the demand for the memory card as well as its application field have been drastically expanded.
Coupling systems between this memory card and a terminal equipment can be broadly classified into a pin plug-in system and a non-contact system. The pin plug-in system uses about 68 pins, for example, and can exchange signals. Therefore, it can transfer 8-bit or 16-bit parallel data and can make high speed read and write data. However, because a surface of a connector (conductor) is exposed, this system involves the drawbacks that contact defect is likely to occur due to contamination by dust and oils, and plug-in/out resistance drops with miniaturization of the pins.
The latter system, that is, the non-contact system, is free from the problems of the former because the conductor is not exposed, and this system can be employed even under a contaminated environment. Therefore, it has been put into practical application in various fields.
An electromagnetic coupling system and a system utilizing light or radiowaves have been proposed as means for supplying power and exchanging signals under a non-contact state. Among them, the electromagnetic coupling system has been put into practical application at present from the aspect of the cost and power consumption.
FIG. 1 is a plan view showing a mounting state of electronic components in a memory card using the electromagnetic coupling system according to the prior art. The drawing shows an SRAM card, by way of example, using the electromagnetic coupling system which is generally referred to as a "sheet coil system". A large sheet coil 101, a plurality of small sheet coils 102a, 102b, 102c, memory ICs 103a, 103b for storing and holding data such as SRAMs, a control IC 104 for controlling data read/write, a cell 105 for holding data recorded in the memory ICs 103a, 103b, etc., are mounted to a printed board 100.
The large sheet coil 101 is a coil for receiving power to the IC card and clock signals, and has a large number of turns and a large diameter so as to receive sufficient power. The small sheet coils 102a to 102c function as a data reception coil 102a, a data transmission coil 102b and a command signal reception coil 102c, for example. These sheet coils 101 and 102 are formed by the same method as the method of forming a conductor pattern which is formed on the printed board 100.
Though not shown in the drawing, the coil of the terminal equipment is disposed at a position at which it opposes the coil of the IC card so that when the line of magnetic force generated by the coil on the terminal equipment side, for example, crosses the coil on the IC card side, an induced current develops on the coil on the IC card side on the basis of the Lenz's law and signal exchange can be thus made.
In the construction described above, data exchange is fully executed by serial signals. Therefore, this system is more disadvantageous in the transfer rate than the contact system which is based on the parallel transfer of 8-bits or 16-bits.
Incidentally, parallel transfer can be attained by increasing the number of coils. However, because the occupying area is generally about 100 mm.sup.2 for the small sheet coils and about 400 mm.sup.2 for the large sheet coil, the sheet coils can be increased only at the sacrifice of the mounting areas of other electronic components, and a greater memory capacity is impeded.
FIG. 2 is a plan view showing the mounting state of electronic components, and mitigates the problems with the prior art example shown in FIG. 1. (Refer, for example, to JP-A-3-232207.) In the drawing, reference numerals 106a to 106i denote thin film coils, and reference numeral 107 denotes a thin film coil module containing these thin film coils 106a to 106i.
This construction is directed to 8-bit parallel transfer and uses a thin film coil module 107 including nine thin film coils 106, that is, eight thin film coils 106a to 106h for data transmission/reception and one thin film coil 106i for receiving a command signal.
As described above, miniaturization can be attained by using a plurality of thin film coils 106a to 106i, and 8-bit parallel transfer can be executed without much increasing the occupying area of the coils.
According to these prior art devices described above, however, the coils for effecting data exchange and supply of power by electromagnetic coupling are formed on, or mounted to, the same substrate with other electronic components such as a memory IC, a control IC, etc. After all, the number of electronic components mounted or their mounting form imposes limitation, and this construction is not suitable for accomplishing higher functions and greater capacity of the IC card.
As described above, the IC card of the electromagnetic coupling system and the pin plug-in system IC card have both merits and demerits. Therefore, they have been developed and designed in accordance with the object of their use or application. In other words, unnecessary time has been spent for the development and design, the printed wiring board cannot be used in common, and the production cost increases eventually.
The prior art technology described above has been designed on the premise that mutual interference does not exist between parallel transmission lines. If the parallel transmission lines are close to one another with small gaps when signal transfer is effected by a magnetic flux or light, for example, magnetic or optical interference occurs between the transmission lines and correct signal transmission cannot be made. In other words, according to the prior art technology, the transmission lines are spationally spaced apart from one another to such an extent that mutual interference between them can be substantially neglected. Accordingly, a higher density cannot be accomplished by bringing the transmission lines closer to one another beyond this limit.